1. Field of the Invention
The present invention relates to a twin wire former in a machine for the production of a fiber web, and, more particularly, to a twin wire former for the production of a paper or cardboard web from at least one fiber stock suspension.
2. Description of the Related Art
A twin wire former, generally also referred to as a vertical former is known, for example, from the Voith German patent application DE 40 14 403 A1 (PB06623 DE) and the Voith European patent application EP 0 454 989 A1 (PB06623 EP). At the exit of the vertical forming section, that includes forming elements, the twin wire runs over an open forming roll such as a suction couch roll. The function of this suction couch roll is to further increase the dry content in the forming fibrous web.
A disadvantage of utilizing a forming roll, that is configured as a suction couch roll, is that the initial investment, as well as the operating costs, typically energy costs for its drive and for an air supply are expensive. Also this construction is maintenance intensive at a level that is above average. Additionally, the suction couch roll must generally also be equipped with special cleaning systems and it exhibits an increased noise level during operation. The suction couch roll is a heavy sub-assembly for the frame. With wide machine widths the suction couch roll is a deflection prone sub-assembly for the wire segment, and is a critical cause for suction roll shadow marks that lower fiber web quality.
What is needed in the art is a twin wire former with improved drying characteristics.